1. Field of the Invention
The invention is directed to a modular drive axle having a sliding gear transmission.
2. Description of the Prior Art
A conventional power train for a work vehicle comprises a prime mover or internal combustion engine applying rotary motion to a main clutch. The main clutch engages a transmission which manipulates the speed of the rotary motion. The transmission in turn is coupled to a differential which applies the rotary motion to right and left axles. The axles are provided with final drives for driving wheels that propel the vehicle. In work vehicles the final drives may comprise planetary reduction units.
Hydrostatic drive systems provide an infinitely variable method of adjusting the speed of the final drives. In a hydrostatic drive system the internal combustion engine drives a fluid pump which supplies fluid to a fluid motor. The motor in turn is operatively coupled to the final drives for driving the vehicle. The pumping unit can be a reversible variable displacement pump, so that the operator by adjusting the position of the swash plate can drive the vehicle at any speed over a specified range, in forward or reverse.
The hydrostatic drive only operates efficiently over a limited speed range, as such shiftable transmissions have been added between the hydrostatic motor and the final drives to increase the efficient range of the hydrostatic unit. More specifically, on combines the hydrostatic units have been provided with four-speed transmissions to increase the effective speed range of the combine.
One type of mechanical transmission is the collar shift transmission. The collar shift transmission has parallel shafts with gears in constant mesh. In neutral, the gears are free-running but when shifted, they are locked to their shafts by sliding collars. When a gear is engaged, it is secured to its shaft by a collar or coupling device. The gear is disengaged when the collar is released and the gear turns freely again.
To insure that the gears are correctly held in place, it is known to angle the side surface of the gear tooth and the root of the sliding gear so that the gear is biassed against a stop during rotation. It has been found that the canted surfaces need be only five to seven degrees.